A wide variety of spark-erosion machines are known in the prior art. Such machines are used for example to generate bores. In such cases for example ceramic tubes are used as electrode guides or carbide collet chucks with side tensioning mechanisms are used. With these known electrode guides, the tolerances of the tensioned position of the electrode in relation to the axis of rotation are around 5 μm, which means that they are relatively inaccurate for the generation of microbores.
The production of microbores is particularly problematic and so in particular is the production of conical microbores with accurately defined front or rear widening. It has not as yet been possible to mass-produce such microbores with an acceptable tolerance of 1 μm. Conical microbores in particular can only be generated subject to adjustments to the erosion parameters. For example conical bores are generated by means of a removal capacity that increases with the depth of the bore or a rotating wire electrode is energized to oscillate as the depth of the bore increases, in order to describe a cone shaped path. However with such methods only bores with inaccurate dimensions and relatively large tolerances of over 5 μm can be obtained. For example when producing microbores for fuel injection valves, tolerances in the range of 1 μm would be desirable. There is therefore a need for an electrode guide and a spark-erosion method which achieve such tolerances of 1 μm.